Genetic Variability among Cowpea (Vigna unguiculata L. Walp) Mini Core Collection
Toyin Osho
Pan African University Institute for Life and Earth Sciences (Including Health and Agriculture), University of Ibadan, Ibadan, Oyo State, Nigeria.
Bunmi Olasanmi *
Department of Agronomy, University of Ibadan, Ibadan, Oyo State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Aims: To evaluate cowpea genotypes selected from mini core collection for variability that can be exploited in breeding programme and also to provide information on high yielding genotypes to aid further use of the genotypes in cowpea improvement programmes.
Study Design: A completely randomized design in two replications was used for the study.
Place and Duration of Study: International Institute of Tropical Agriculture (IITA), Ibadan, Oyo State, Nigeria between March and August, 2017.
Methodology: Two hundred cowpea genotypes were grown in the glass house at IITA. Data were collected on twelve agronomic characters including plant height, chlorophyll content, days to first flower initiation, days to first pod harvest, hundred-seed weight, pod length, number of pods per plant, mean number of seeds per pod, grain yield per plant, seed length, seed width and seed thickness. The data were subjected to analysis of variance, cluster and principal component analyses.
Results: Significant genetic variability was observed among the cowpea genotypes for all the agronomic characters investigated in this study. The genotypes were grouped into five clusters with TVu1059 and TVu43 identified as the most distinct. The first four principal components (PC) with eigen values > 1 accounted for 72.5% of the total variation among the cowpea genotypes with loadings of hundred-seed weight, seed length, seed width, seed thickness, days to first pod harvest, days to first flower, pod length, mean number of seeds per pod, pods per plant and grain yield per plant.
Conclusion: The broad genetic variation observed among the cowpea genotypes evaluated in this study for yield and yield-related characters can be explored to improve cowpea.
Keywords: Cowpea mini core collection, principal component analysis, cluster analysis, agronomic characters of cowpea.